The Founding of the Roman Empire and Its Expansion to 100 B.C.E. Beginning in the 330s B.C.E., Rome, a city-state located on the Tiber River in central Italy, took the first military actions to unify the Italian peninsula. By the early third century B.C.E., Rome had annexed all of Italy; the western Mediterranean islands of Sicily, Sardinia, and Corsica; and the Iberian Peninsula. It established territorial provinces under the command of former military leaders. Over the next century, the new empire added five more coastal provinces by conquering parts of North Africa, southern France, and the Aegean seacoast. This map depicts the early Roman Empire as a littoral polity, organized around river and ocean travel and around the control of islands, port cities, and coastal lands.

The Expansion of the Roman Empire from 100 B.C.E. to 14 C.E. Over the second century B.C.E., the Roman Empire grew beyond its Mediterranean coastal core. In two phases of territorial expansion, the empire moved inland into Europe, the Nile valley, and central Anatolia. It also added additional coastal territory along the southern coast of the Black Sea, the Adriatic Sea, and the southern and eastern Mediterranean. By the time it reached this extent, the empire had conquered dozens of formerly isolated cultural entities—with their unique practices, languages, and religions—to create a single political and economic entity. The Roman Empire fostered cultural sharing and trade, although it responded to resistance with violent suppression.

The Expansion of the Roman Empire after 14 C.E. In its final era of expansion, the Roman Empire added provinces at its peripheries. Many of the new territories had harsh climates and terrains. Others had robust imperial traditions of their own. Unlike with the earlier conquests of coastal territories and river valleys, securing and governing the new lands involved long and difficult journeys to and from the capital. With the addition of Britain, eastern Anatolia (followed later by Armenia and Mesopotamia), eastern Germany, the Carpathian Mountains, and the Arabian Peninsula, the Roman Empire spanned five time zones on the modern map. Its territory tested premodern forms of communication and transportation and strained political and military limits. The empire soon would begin to split and contract.

Roman Roads, Cities, and Fortifications. To administer an empire of such great size, the Roman government made a significant investment in infrastructure. An extensive network of roads (paved in many places and with distance markers) and well-traveled sea lanes ensured that merchants, armies, and other travelers could move efficiently and predictably around the empire. Major cities—ports, provincial capitals, and other entrepots—flourished at highway intersections and along coastlines and navigable rivers. Defensive walls and military garrisons—a massive military investment—marked the frontiers of the empire and the effort to defend its territory from both domestic rebels and foreign invaders.

Roman Trade. The unified Roman Empire offered stable and predictable conditions for trade: a shared economic and legal system, reasonably secure transportation, and a government that spent money on goods and salaries. This map depicts how some goods circulated throughout the empire. Ocean products traveled from the coast to inland cities and garrisons, while grains, wine, and olive oil traveled from farms to coasts, deserts, and mountains. Slaves from the eastern European frontier were sent to distant plantations and garrisons. Minerals, marble, gems, and manufactured goods such as ceramics traveled in all directions from the places where they were produced or acquired.